JPH04289788A - Motor starting circuit - Google Patents

Abstract

PURPOSE:To obtain a motor starting circuit in which power consumption and thermal influence onto peripheral components can be suppressed, reset time to restart is shortened, and lifetime of PTC element can be prolonged. CONSTITUTION:Auxiliary winding 13 of a motor 11 is connected in series with the relay contact 14a of a voltage type electromagnetic relay 14 and connected in parallel with a relay winding 14b. Furthermore, a PTC element 15 is connected in series with the relay contact 14b in order to detect variation of voltage to be applied on the auxiliary winding 13 by means of the relay winding 14b. When the voltage being applied on the auxiliary winding 13 exceeds a predetermined level, the relay contact 14a is opened to interrupt current supply to the PTC element 15.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a circuit for starting a motor having a main winding and an auxiliary winding.
Voltage type electromagnetic relay and positive temperature coefficient thermistor element (hereinafter referred to as P
The present invention relates to a motor starting circuit configured using a TC element (abbreviated as TC element).

0002

2. Description of the Related Art FIG. 2 shows an example of a conventional motor starting circuit. The motor 1 has a main winding 2 and an auxiliary winding 3, and a voltage type electromagnetic relay 4 is connected to the motor 1. That is, the relay contact 4a of the voltage type electromagnetic relay 4 is connected to the auxiliary winding 3 in series. In addition, electromagnetic relay 4
The relay winding 4b is connected to the auxiliary winding 3 in parallel. Note that 5 indicates a starting capacitor, 6 indicates a power supply, and 7 indicates a switch. However, in the motor starting circuit shown in FIG. 2, since a relatively large current flows through the relay contact 4a, defects such as burn-out of the contact tend to occur.

[0003] Therefore, as shown in FIG. 3, a motor starting circuit using a PTC element has been used. In the motor starting circuit shown in FIG. 3, a PTC element 8 and a starting capacitor 5 are connected in series to the auxiliary winding 3. Here, current flows through the main winding 2 and the auxiliary winding 3 by closing the switch 7, but the PTC element 8 self-heats and its resistance value increases rapidly. Therefore, the structure is such that the current flowing through the auxiliary winding 3 is rapidly reduced as the resistance of the PTC element 8 suddenly increases.

0004

[Problem to be solved by the invention] However, PTC
Even in the motor starting circuit using element 8, as shown in FIG. 4, the current flowing through the PTC element does not become zero even after entering rated operation, but continues to flow as a residual current. Therefore,
Since residual current continues to flow through the PTC element 8, there is a problem in that extra power is consumed. In addition, since the residual current flows and the PTC element 8 continues to generate heat, it is impossible to restart the PTC element 8 even if the switch 7 is turned off until the PTC element 8 cools down. That is, there was a problem in that a relatively long recovery time was required before restarting.

[0005]Furthermore, since the PTC element 8 continues to be in a heat generating state as described above, components disposed around the PTC element 8 may be adversely affected by heat. In addition, since the voltage is applied to the PTC element 8 for a long time, this becomes a factor that shortens the life of the PTC element 8. Therefore, an object of the present invention is to eliminate the drawbacks of conventional motor starting circuits using PTC elements, reduce power consumption and adverse thermal effects on surrounding components, and shorten the recovery time until restart. Another object of the present invention is to provide a motor starting circuit which can extend the life of a PTC element and has a structure in which contact failures are less likely to occur as in motor starting circuits using conventional electromagnetic relays.

[0006]

SUMMARY OF THE INVENTION The present invention is a circuit for starting a motor having a main winding and an auxiliary winding,
It is characterized by having the following configuration. That is, a voltage-type electromagnetic relay is provided that has a relay contact connected in series to the auxiliary winding and a relay winding connected in parallel to the auxiliary winding. This electromagnetic relay is configured so that the state of the relay contact can be switched between an open state and a closed state by detecting a change in the voltage applied to the auxiliary winding. That is, when the voltage applied to the auxiliary winding is below a predetermined value, the relay contact is closed, and when it exceeds a predetermined value, the relay contact is opened. In addition, the relay contact of the above electromagnetic relay is
PTC elements are connected in series.

[0007]

[Operation] The present invention is characterized in that a voltage-type electromagnetic relay and a PTC element are used in combination. In other words, since the PTC element is connected in series to the relay contact of the electromagnetic relay, when the relay contact of the electromagnetic relay is opened after startup, the current flowing to the PTC element is cut off, thereby causing the current to flow to the PTC element. This solves the problem of conventional starting circuits due to continuous flow of . On the other hand, since the PTC element is connected in series to the relay contacts of the electromagnetic relay, the current flowing through the relay contacts is reduced, thereby solving the problem of contact failure in conventional starting circuits using only electromagnetic relays.

[0008]

[Description of Embodiment] FIG. 1 shows a C as an embodiment of the present invention.
FIG. 3 is a diagram showing an SR type motor starting circuit. The motor 11 has a main winding 12 and an auxiliary winding 13, and a voltage type electromagnetic relay 14 is connected to the motor 11. That is, the relay contact 14a of the voltage-type electromagnetic relay 14 is connected in series to the auxiliary winding 13, and on the other hand, the relay contact 14a of the voltage type electromagnetic relay 14 is
b is connected in parallel to the auxiliary winding 13. This voltage type electromagnetic relay 14 detects the voltage applied to the auxiliary winding 13 with a relay winding 14b, and when the voltage is below a predetermined value, closes the relay contact 14a and exceeds the predetermined value. and is configured to be in an open state. Further, a PTC element 15 and a starting capacitor 16 are connected in series to the relay contact 14a. In addition, 17 is the power supply, 18
19 indicates a switch, and 19 indicates an operating capacitor.

Next, the operation of the motor starting circuit of this embodiment will be explained. First, in the state before startup, since no voltage is applied to the auxiliary winding 13, the relay contact 14a is in a closed state. By closing switch 18, a starting current flows through main winding 12 and auxiliary winding 13. Therefore, the PTC element 15 starts self-heating. PTC element 1
In No. 5, the resistance value rapidly increases with heat generation and approaches the rated operating state. As a result, the auxiliary winding 13 is excited,
The applied voltage increases. When the voltage applied to the auxiliary winding 13 exceeds a predetermined value, the relay winding 14b opens the relay contact 14a, cutting off the current supply to the auxiliary winding 13 and the PTC element 15 side. Therefore, since the current supply to the PTC element 15 is cut off after the activation is completed,
No power is consumed in the PTC element 15 after activation is completed. In addition, due to the interruption of the current, the PTC element 15
Since the heat generation also stops, the temperature of the PTC element 15 is gradually lowered. Therefore, it is possible to shorten the recovery time until the motor 11 is started again after the end of the rated operation. Furthermore, since the period during which the PTC element 15 is in a heat generating state is shortened, there is less risk of adverse thermal effects on surrounding components, and furthermore, the life of the PTC element 15 itself is extended.

Although the embodiment shown in FIG. 1 shows a circuit applied to the CSR starting method, the present invention can also be applied to a motor starting circuit employing other starting methods. FIG. 5, which shows such examples in FIGS. 5 to 7, is a diagram showing a circuit of an embodiment applied to the CSIR activation method. Here, the relay contact 14a of the voltage-type electromagnetic relay 14, the PTC element 15, and the starting capacitor 16 are connected in series, but the operating capacitor is omitted. Figure 6 shows the RS
FIG. 2 is a circuit diagram of an embodiment applied to an IR activation method. This R
In the SIR starting method, PTC element 1 is connected to relay contact 14a.
5 is connected, but unlike the circuit of FIG. 1, the starting capacitor 16 and the running capacitor 19 are omitted.

FIG. 7 is a circuit diagram of an embodiment applied to the PSC activation method. In the circuit shown in FIG. 7, a starting capacitor is not connected in series with the PTC element 15, but an operating capacitor 19 is connected in parallel with the relay contact 14a and the PTC element 15. 5 to 7 described above, the relay contact 14a and PTC element 15 of the electromagnetic relay 14 are connected in series to the auxiliary winding, and the relay winding 14b is connected to the auxiliary winding 13. Since they are connected in parallel, the PTC
The residual current flowing through the element 15 can be interrupted by the relay contact 14a. Therefore, the same effects as the embodiment shown in FIG. 1 can be achieved.

0012

As described above, in the present invention, the current flowing through the PTC element after startup is caused to open the relay contacts of the voltage-type electromagnetic relay in response to changes in the voltage applied to the auxiliary winding. Since the power is cut off, power consumption can be reduced. In addition, by cutting off the current supply to the PTC element, the PTC element stops generating heat, which is different from the conventional PTC element.
Compared to a motor starting circuit using a TC element, the recovery time up to restart can be shortened. Moreover,
Since the time during which the PTC element is in a high temperature state is shortened, it is possible to reduce adverse thermal effects on surrounding components, and it is also expected that the life of the PTC element itself will be extended.

[0013] Furthermore, in conventional motor starting circuits that use only voltage-type electromagnetic relays without using PTC elements, defects such as burn-out of contacts tend to occur due to the flow of large currents, but in the present invention, Since the PTC element is combined with the electromagnetic relay, it is possible to prevent arc discharge and spark discharge when the contacts break, thereby preventing defects such as burning of the contacts of the electromagnetic relay, thereby extending the contact life. It is also possible. Furthermore, compared to a motor starting circuit that uses only voltage-type electromagnetic relays, PTC
Since the resistance of the element itself is added, it is possible to reduce the cost of the auxiliary winding of the motor.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a motor starting circuit according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a conventional motor starting circuit.

FIG. 3 is a circuit diagram showing another example of a conventional motor starting circuit.

FIG. 4 is a diagram showing temporal changes in current flowing through a PTC element in the motor starting circuit of FIG. 3;

FIG. 5 is a diagram showing a motor starting circuit of an embodiment applied to the CSIR starting method.

FIG. 6 is a circuit diagram of an embodiment applied to the RSIR activation method.

FIG. 7 is a circuit diagram of an embodiment applied to a PSC startup method.

[Explanation of symbols]

11...Motor 12...Main winding 13...Auxiliary winding 14...Voltage type electromagnetic relay 14a...Relay contact 14b...Relay winding 15...PTC element

Claims (1)

[Claims] Claim 1: A circuit for starting a motor having a main winding and an auxiliary winding, the circuit comprising a relay contact connected in series with the auxiliary winding and a relay winding connected in parallel with the auxiliary winding. a voltage type electromagnetic relay that closes the relay contact when the voltage applied to the auxiliary winding is below a predetermined value and opens the relay contact when it exceeds the predetermined value; A positive temperature coefficient thermistor element connected to a motor starting circuit.